The principle objective of this project is to deduce the physical bases of signal processing in the inner ear, the understanding of which will be essential to rational attacks on inner-ear pathologies. The immediate goal of the research is identification of specific structure-function correspondences in the inner ear. Such correspondences are expected to be rich in implications regarding the physical mechanisms underlying vestibular and auditory signal processing. We study inner-ear microstructure with conventional light microscopy, scanning electron microscopy, and transmission electron microscopy, and with low temperature scanning electron microscopy specially adapted to studies of fragile inner-ear structures. Functional parameters of individual nerve fibers are identified electrophysiologically, with dye-filled microelectrodes advanced into the eighth nerve after its emergence from the intact inner ear. After identification, the fiber is injected with dye and traced to its starting points in the ear. Thus, we obtain precise functional overlays for our microstructural maps. In addition, we observe microstructural parameters of the fiber itself. Our principal working hypothesis is the existence of functional consequences for the several conspicuous parameter variations known to occur in the microstructures of the nerve fibers and their associated sensory surfaces. Because of the functional and structural similarities between the inner ear of the bullfrog and that of mammals, and because of the extensive background information available on the frog's ear, we use the frog as our experimental model.